The SCaN Testbed flight software resides in the Avionics subsystem
and the three Software Defined Radios.

Avionics Subsystem Software

The avionics software runs on the single-board computer to:

process commands
provide thermal monitoring and control
communicate with the radios and ISS
command and configure the radios
control RF subsystem switching
command the APS
collect sensor data
send telemetry to the ground
perform data and file management
Software development for the Avionics subsystem is the responsibility
of GRC.

Software Defined Radio Software

Each of the three SDRs has an Operating Environment (OE),
which includes an operating system and provides infrastructure
services to applications and waveforms. In addition to the
OE, each SDR must run Waveforms, which implement the unique
capabilities of the radio to receive and transmit RF signals,
provide networking capability, and do navigation and timing.
Each radio will have an initial experimental waveform, in addition
to test waveforms developed by the radio supplier.

Software which will be loaded into the Avionics Subsystem,
which directly interfaces with the ISS and which is responsible
for safety critical functions, is and will be developed in
accordance with NASA Class C. Any reconfigurations/updates
to any individual or combination of the SDRs default version
will be developed and implemented in accordance with Class
E procedural requirements as stated in NPR 7150.2, NASA Software
Engineering Requirements, as a minimum, plus selected augmented
Class D requirements as supplied by NASA and negotiated between
NASA and the Experimenter. Experimenter developed software
in the radios will not be Class C, but will require some verification
to insure that safety requirements are met.

During the operations phase, radios and the avionics package
can be reconfigured from the ground with new software. Software,
here, means both that which is running on a processor in the
radio, and the configuration of in-flight reconfigurable Field
Programmable Gate Arrays (FPGAs). There are no in-flight reconfigurable
FPGAs in the Avionics Subsystem.

Ground System Software

The Ground System software is developed by GRC in accordance
with NPR 7150.2 NASA Software Engineering Requirements and
the procedural requirements it specifies for NASA Class C software.
Primary path ground software utilizes the NASA Telescience
Resource Kit (TReK), a suite of PC-based software applications
used by scientists and engineers to monitor and control payloads
on-board the International Space Station

Waveforms

Waveform software and firmware defines functionality for most
of the SDRs. STRS defines standards for SDRs to maximize waveform
firmware and software reuse and reduce porting effort between
various radios. All three SCaN Testbed radios will be launched
with baseline STRS-compliant waveforms.

Refer to the SCaN Testbed Flight and Ground System Description
(in the Candidate Experimenter Info Tab) for more information
about waveforms and waveform updates.

Software External Interfaces

The SCaN Testbed software interfaces externally with the ELC
via the 1553 interface and the Ethernet interface as shown
in Figure 9. The Ground System interfaces with the Enhanced
Huntsville Operations Center (EHOSC) through the GRC Telescience
Support Center (TSC) and the NASA Integrated Services Network
(NISN)/Internet Protocol Operations Network (IONet) as shown
in Figure 10.